Static pressure measuring tube



' Sept. 19, 1939. H. KARLSSON ET AL;

STATIC PRESSURE MEASURING TUBE Filed May 24, 1938 INVENTORS 17111110" flarlsson BYJ0sy4i1 Wzillus a l w Patented Sept. 19, 1939 I a g .jgumTs-o STATES PATENT OFFICE STATIC PRESSURE MEASURING TUBE Hilmer Karlsson and Joseph Waitkus, Wellsville,

N. Y., assignors to The Air Preheater Corporation, New York, N. Y.

Application May 24, 1938, Serial N0. 209,676

4 Claims. (01. 7331) Our invention relates to measuring devices and a gas stream and a manometer connected to particularly to improvements in apparatus for tubing 53 will then indicate the static pressure measuring the static pressure of a gas flowing existing in the gas flowing along the surface oi through a flue. tube H through the chamber E6. The gas enters 5 In measuring the pressure of a gas stream, slots l5 and flows through the annular chamber 5 difiiculty is frequently encountered in obtaining it as a narrow film over the apertures l8 in the a true static pressure reading because at least Wall of tube H to exit from the open end of tube part of the velocity head or impact pressure of H3 or vice versa. In addition to spacing the the gas stream is added to or subtracted from the tubes the fins near the end of the device alsotrue static pressure. This is particularly true obviate any eddy currents or spiraling motion in 10 in obtaining a reading of gas flow through air the gas flowing between the tubes. The apparatus preheaters where conditions encountered include may be inserted in the gas stream at any angle bends and changes in the cross section of the gas to the direction of flow of the gas and it is also duct, all contributing to produce a turbulent gas immaterial whether the gas flows from the slots stream. l toward the open end of tube or in the op- The main object of the invention is to provide posite direction because the pressure measured apparatus for measuring the static pressure in a is that exerted by an undisturbed film of gas flowgas stream which will not be affected by the veing over the small openings I8 in the smaller locity of the gas. tube I I.

In the drawing, The apertures 18 in tube H are preferably 90 Fig. 1 is a longitudinal sectional view, partly, spaced from the location of the slots IS in the broken away, of a static pressure measuring aplarger tube ID by a distance five times or more paratus embodying our invention. the mean diameter of the free area between the Fig. 2 is an end view of the apparatus; and tubes so that any disturbance produced as the Fig. 3 is a cross-sectional view on the line 3-3 gas changes direction by ninety degrees in enterof Fig. 1. ing or leaving through the slots [5 is not com- Our improved static pressure measuring device municated to the apertures l8 in the inner tube, comp-rises a pair of concentric tubes H), H, the the arrangement providing a narrow film of gas larger tube l0 being open at one end while its passing over the aperture or apertures in the opposite end is closed by a cap l2. One end of smaller tube. The total area of the openings or the smaller tube 1 extends beyond the cap l2 on slots l 5 in the wall of the outer tube I0 is prefertube In for connection by tubing l3 to a manomably two and a half times or more the area of the eter or other gauge (not shown) suitable for indiannular space l5 between the tubes so that any eating static pressure. The opposite end of the disturbance resulting from a change in velocity smaller tube I0 is closed as indicated at I 4. The effect in entering or leaving the annular space 355 tubes 50, II are maintained spaced to form an between the tubes may be eliminated.

annular chamber l6 between them by several sets Although an illustrative embodiment of our of a a y eXtending fins 17 secured to d Spaced invention has been described and shown in detail v ly above the Smaller tube herein it is to be understood that many changes The Wan of the larger tube is formed with and variations may be made without departing one or more apertures to provide flow of gas from the invention and therefore it is desired giggi g? g gggi i gg fi w fia ga 3 3; and intended to include all such changes and apertures are employed, they are spaced evenly 3 12 wlthm the Scope of the appended about the circumferenceof the tube 10 as shown a We claim is: i l iiiti'l giii t dil il sit oi ifi 'ififiii ite Appamtus F r measuring the static Pressure- Wall of the smaller tube H is formed with one or of gas compnsmg tube f f be more small apertures l8 at a location spaced ax- W end to a pressure mdlcator ially of the assembly from the position of the havmg its slde Wall formed at a pomt axially slots l5 in the wall of the surrounding tube Ill. As Spaced from Said end with e ore apertures; shown two apertures l8 are formed at diametrimeans Closing the other end of Said e; a Seccally located positions in the wall of tube II but 0nd tube surrounding said first mentioned tube spaced axially thereof from each other. in spaced relation to provide an annular chamber In operation the apparatus is projected into and. having its side wall formed with an aperture ture of larger size than the aperture in said first mentioned tube and spaced axially therefrom; and longitudinally extending spacing members disposed circumferentially about the first mentioned tube to space the second mentioned tube therefrom, said members being lo-.

cated in positions spaced axially from the apertures in both tubes.

3. Apparatus for measuring the static pressure of a gas comprising a tube adapted to be connected at one end to a pressure indicator and formed at a point axially spaced from said end with one or more apertures; means closing the other end of said tube; a second tube surrounding said first mentioned tube in spaced relation to provide an annular chamber and formed with a pair of diametrically located, axially extending slots spaced axially from the apertures in said first mentioned tube.

4. A device of the type described comprising a pair of concentric tubes each having several circumferentially located apertures formed in their walls, the apertures in the wall of tthelarger tube being of greater area than those in the smaller tube and spaced axially therefrom; means closing one end of the smaller tube; means for connecting the opposite end of the smaller tube to pressure indicating apparatus; and means spacing said tubes to form an annular chamber through which gas may pass to flow across the apertures in the smaller tube in a path between the apertures in the larger tube and the end thereof adjacentthe closed end of the smaller tube when the assembly is projected into a gas stream to expose the apertures in the larger tube.

HILMER KARLSSON. JOSEPH WAITKUS. 

